Physical Oceanography Division

BENCHMARKS

FOR ATLANTIC OCEAN CIRCULATION

Lower layer The Deep Western Boundary Current: The DWBC provides the main conduit for waters formed in the subpolar and polar Atlantic to the South Atlantic and then on to the other ocean basins.  As surface forcing functions change in the formation regions for the DWBC water masses, the characteristics of the water masses will vary downstream.  Tracking these changes provides a benchmark for evaluating model simulations of the advective times from the formation regions.  For example, a water mass formed in the Labrador Sea (LSW) is advected in the DWBC to 26.5N, east of Abaco Island, the Bahamas. Time series of the characteristics of LSW at Abaco provide a benchmark for present day advective time-scales from source to subtropical western boundary.  • Decadal Signal: Temperature and salinity characteristics at the depth of LSW in the DWBC at 26.5N are shown in the figure . (This time-series will be updated as additional data is collected.)  Showing late-90 cooling and freshening.  This changes can be correlated to changes in the characteristics of LSW at it’s formation region.  The comparison indicates the arrival of LSW at Abaco some 8 to 10 years after formation in the Labrador basin . These advective times are somewhat shorter than previously hypothesized (Molinari et al., 1998) but consistent with other observations obtained in the central subtropical and eastern mid-latitude Atlantic. . Time series of T, S and depth along a density surface representing the Labrador Sea Water obtained from historical data collected east of Abaco Island, Bahamas. A pronounced cold, fresh pulse of Labrador Sea water appeared in 1995, less than eight years after it was produced in the Labrador Sea. Results indicate a faster “Conveyor Belt” than previously thought.   References: Molinari, R.L., R.A. Fine, W.D. Wilson, R.G. Curry, J. Abell and M.S. McCartney (1998). The arrival of recently formed Labrador Sea Water in the Deep Western Boundary Current at 26.5N, Geo. Res. Let., 25, 2,249 - 2,252. . . . << Back